Goals of achieving energy independence and concerns about depleting fossil fuel reserves and environmental impacts of energy generation has stimulated a lot of interest in research in the area of renewable and sustainable energy. Wind power is one of the fastest growing renewable technologies in the world at present. The United States with 35 GW of installed wind capacity in 2009 has the goal of achieving 20% wind power penetration by 2030. Increasing wind penetration into existing power grids in turn increases the problems caused by the inherent variability and uncontrollable nature of the wind resource. Since the system loads are also variable and represented by forecasts, balancing supply and demand for electric power is becoming increasingly difficult.
Addressing the issues of variability of wind power by incorporating energy storage units operating in combination with wind farms is an attractive idea. A number of wind to storage projects are also being planned and implemented across the U.S. However, a question that is often unaddressed is the optimal size of the required storage unit for a given system. This work proposes a methodology to compute the optimal storage size required for a system consisting of wind generation and load.
One of the main characteristics of renewable power such as wind and solar is the inherent variability and uncontrollability. Even with state-of-the art forecasting techniques, actual generation can be substantially deviated from the forecasted values. In addition, the system load is also variable and needs to be forecasted ahead of time for unit commitment and system planning and operation purposes. Although daily loads follow a pattern, every forecast is associated with a certain degree of uncertainty. In a system consisting of only renewable generation and load, with minimum or no connection to the grid, the task of energy balancing is extremely difficult. Incorporation of energy storage units is being considered as a possible solution to this problem. However, energy storage units till date are expensive. Hence the question that arises is, given a generation-load system, what is the optimal amount of storage required. This invention investigates the storage size required by a system consisting of a renewable generation and a load in meeting certain specified reliability indices and considering the forecast uncertainties.
The incorporation of forecast uncertainties into processes such as generation scheduling, load following, is critical for improving system performance, maintaining system reliability, and minimizing expenses related to the system balancing functions. However, the power system demand and supply balancing process is traditionally based on deterministic models. Scheduling and load following processes use load and wind power generation forecasts to achieve future balance between demand and supply of electric energy. Since the actual load and wind generation can deviate from their forecasts significantly, with increasing penetration of renewable resources, it becomes increasingly difficult to guarantee whether the system would actually be able to meet the required reliability criteria. Hence, it is important to address the uncertainty problem by including the sources of uncertainty including forecasts of load and wind generation into consideration. In this work, a methodology has been presented for incorporating uncertainties associated with wind and load forecast. The consideration of uncertainties is a unique feature that makes this work a significant step forward toward the integration of renewable resources such as wind.